Petroleum-contaminated sites pose a serious threat to public health and the environment. In order to remove the petroleum contaminants and restore the subsurface, reliable in-situ bioremediation technologies are needed. However, the efficiency of bioremediation decreases significantly when applied to western Canadian cases because of the special natural conditions, such as cold climate and low-permeability soils. This gap needs to be filled in order to provide sound approaches for the petroleum industry and government organizations.

In this research, a set of innovative biosurfactant-enhanced in-situ bioremediation methodologies and associated technologies have been developed to improve both microbial activities and media (soil) conditions within the western Canadian context. The following issues are addressed:​ (a) screening, regeneration, and re-enhancement of specific cold-adapted naphtha-degrading bacteria;​ (b) investigation of interactions among site inherent microorganisms, isolated cold-adapted strains and co-cultured biosurfactant-producing bacteria during naphtha degradation for helping obtain appropriate strains for biosurfactant production;​ (c) optimization of materials and conditions for biosurfactant production using naphtha as a sole carbon source;​ (d) optimized biosurfactant production and characterization;​ (e) examination of the performance of newly-developed biosurfactants and related methodologies under various conditions through bench- and batch-scale reactor systems;​ and (f) facilitation of biosurfactant-enhanced bioremediation actions through a custom-designed pilot-scale system to scale-down real contaminated sites in the laboratory.

The major contribution of this research is the advancement of integrated biosurfactant-enhanced bioremediation approaches, which is achieved through a sound technological development, an adapted product generation and an in-depth mechanism investigation. It has been demonstrated that these integrated approaches are capable of enhancing the bioremediation of petroleum-contaminated sites in western Canada. Furthermore, a site-oriented methodology has been put forward and applied throughout the study for effectively reflecting the reality, complexity and dynamics of the subsurface conditions. Real-site soils are selected to screen microorganisms and conduct bench- and batch-scale experiments;​ real-site contaminants are applied as carbon sources for microbial screening and biosurfactant production;​ and, real-site subsurface geological and hydrological conditions are scaled down in the pilot-scale bioremediation system. Also conducted in this research is the design and application of a multi-scale (bench-, batch- and pilot-scales) infrastructure for the examination of biosurfactant-enhanced bioremediation actions. The system can effectively facilitate both the scale-down of site conditions into laboratory systems and the scale-up of experimental results to field applications, thus demonstrating the applicability and effectiveness of the developed methodologies and further facilitating technology transfer. Generally, this dissertation provides a useful means for bioremediation enhancement and improves the in-depth understanding of the mechanisms for bioremediation processes. The research outputs will be useful for subsurface petroleum contamination remediation in western Canada.